This lesson begins with a simulation of just how quickly an infectious disease can spread through a population, examines the spread of a sexually transmitted disease documented by the video "The Lost Children of Rockdale County," and ends with a survey of the role of the Centers for Disease Control and Prevention (CDC).

* To make 100 ml of 0.1M sodium hydroxide, add 0.4 grams of sodium hydroxide to 100 ml of distilled water OR add 10 ml of 1.0 M solution of sodium hydroxide to 90 ml of distilled water.
Teaching Strategy:

1. Before students arrive in class, half-fill a clear plastic cup with water for each student in the class. To one of the cups, instead of water, add diluted sodium hydroxide solution. Provide each student with one cup of clear liquid and one empty cup.

Tell students that the class will be doing a little role playing to start off the day. They are going to pretend that they are all at a party and they are going to "make contact" with three other people at this party. But the rules for "making contact" are very specific. Explain these rules carefully, and quiz them for understanding before you begin.

Pour half of your liquid into empty cup, then set the remaining liquid aside for later.

To "make contact," pour your liquid into another's cup of liquid.

Swirl the cup and then pour the liquid back into your cup.

Swirl it again and then pour half of the liquid back into your partner's cup.

Keep track of each individual with whom you make contact.

2. Allow the students to "make contact" with three other students in the class. This will work best if movement is allowed and students interact with students from the other side of the class. Be sure they keep a list of with whom and in what order they made contact.

3. After the exchange has taken place, have students return to their seats, and announce that it is a week later, and the health department is concerned. Several students have contracted a disease, and all students who attended "the party" must be tested for this disease.

To determine if an individual has been "infected," a drop of phenolphthalein is added to each exchange cup. If the solution turns pink, the person in control of that cup is infected. If the color does not change, the student is not "infected." Depending on class size and how much "mingling" actually occurred, the results should be fairly dramatic, with twenty-five percent to possibly more than fifty percent of the class ending up infected.

4. Inform the class that only one infected person came to the party, and now it's time to try to determine who that was. Make a class chart on the blackboard or overhead as indicated below:

A "+" indicates a positive response (color change), a "-" indicates a negative (no change). Each student should be listed and then each of his or her contacts in order.

Student

+ or -

exchange #1

exchange #2

exchange #3

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

Eliminate the "un-infected" individuals and try to trace the transmission of the disease back to the original infected person. Once the class has guessed who started the disease, you can verify the results with a drop of phenolphthalein in the cups containing the original liquid.

5. Discuss the results or have students respond to written questions. Possible questions could include:

Were you surprised by the results?

What kinds of disease might be transmitted this way?

What kind of behavior did the liquid exchange represent?

Was it easy to determine the origin of the disease?

How would tracing a disease be different if it were on a larger scale, such as a city, state, or even country?

Is it always important to know the origin of an infectious disease? Why or why not?

How would the results have been different if you exchanged liquids three more times?

How would the results have been different if some students chose not to exchange liquids at all?

6. After discussion or collection of written responses, introduce "The Lost Children of Rockdale County" as a real-life story of the spread of a sexually transmitted disease that affected teenagers. Show the video from the beginning to 09:15. Have students take notes or answer specific questions about the video. Pause the video when it shows the chart constructed by the health department (approximately 05:40) and ask the students how the chart differs from the class's representation of its epidemic. Challenge the students to create their own diagram from the class data collected from the epidemic simulation. Possible questions to ask about the video include:

When did this incident occur?

What was the problem?

What event alerted the authorities to the situation?

What was unusual about this particular outbreak?

How many positive cases of syphilis were recorded?

How many teenagers were exposed to the disease?

Describe the lifestyle or socio-economic status of most of the teens involved in the incidents that occurred.

What was the role of health department?

What did the health department do to stop the spread of syphilis?

Does the behavior in this video surprise or shock you? Why or why not?

Is it possible that such an outbreak could occur in our community?

What should be done to prevent such an outbreak?

7. After discussion of video, and/or collection of students' responses to the questions, ask the students if they have heard of or know anything about the Centers for Disease Control. If there are no responses, explain that it is a federal agency charged with protecting the health and safety of people at home and abroad. The students' task now is to find out more about the CDC. Direct students to the organization's website at: http://www.cdc.gov/aboutcdc.htm. Allow students some time to explore the site and then have them write a brief response to one or more of the following questions:

Briefly describe the history of the CDC.

Choose one of the centers listed under the CDC's organization and describe its function.

Choose one health topic discussed on the site and summarize the information you found.

Explore the data and statistics about STDs or Youth Risk Behaviors and briefly summarize what you've learned.

What kind of career opportunities might one find with the CDC?

Assessments:

Participation in simulation

Participation in discussion or completion of questions after simulation

Video responses

Paragraphs or written summaries of CDC research

Extension:

Have students research the various health organizations available in their own community. What local city, county or state health department services are available? Are there any private or not-for-profit agencies that focus on communicable diseases? How accessible to teens are these agencies or groups?